1. Field of the Invention
This invention relates to locks for closures, especially locks for horizontally sliding closures. More particularly, it relates to devices for double-locking sliding glass doors and windows to prevent their being opened from the outside.
2. Description of the Prior Art
The positioning of rods across the inside of a door to anchor it to a door frame for preventing unauthorized opening from the outside is known. For example, diagonal sliding bolts have been suggested for locking car doors in U.S. Pat. No. 1,335,192. It has been suggested in U.S. Pat. No. 2,854,708 to lock a series of sliding doors together by sliding and bending a rod from one door to wedge against the next one. It is also known to lock garage-type, vertically sliding and folding doors by using bolts which run horizontally across the inside of the door to engage stops in the frame of the building, as shown, for example, in U.S. Pat. No. 3,187,526. Such locks would be visible from the outside if used on glass doors. This is undesirable because it enables a potential intruder to see them and attempt to circumvent the locking means. Locks for burglar-proofing wood or metal swinging doors involving the use of vertical rods are shown in U.S. Pat. No. 3,255,618 and vertical locking rods are also shown built into the structure of a door in U.S. Pat. No. 2,969,666.
In general, these prior art devices suffer deficiencies which render them either too unsophisticated or unesthetic for use with doors and windows in a dwelling place or too complicated for the average homeowner to personally install. Some prior art devices also have many overly sophisticated parts which render their production and installation expensive or they use large parts which are inconvenient for reasonable storage and handling.
It has thus long been felt desirable to provide the art with an inexpensive locking device for sliding glass doors and windows which could be installed by any average person, without any significant mechanical skill. For security and ease of operation, such devices must be designed to double-lock the closure and yet achieve that result with a single locking action. This could be partially achieved using something like the device shown in U.S. Pat. No. 3,255,618 if the cam plate assembly shown therein were somehow reduced in size, e.g., as in the devices shown in U.S. Pat. Nos. 2,969,666 and 2,317,312, to fit on the frame of a typical glass closure. Those devices do provide a double-locking arrangement by a single rotary action of a cam which drives bolts into stops in a surrounding frame. Such devices, however, leave room for improvement. For example, when locking rods or bolts are connected to a rotatable cam plate, as shown in U.S. Pat. Nos. 3,255,618, 2,969,666, or 2,317,312, they not only move axially when the cam is rotated, but they also move transverse to their axes. Even providing a bent section in the rods, as shown in U.S. Pat. No. 2,317,312, cannot eliminate such sideways motion, and it necessarily renders the devices more expensive and complicated to make and assemble.
The presence of transverse motion means that the locking rods must be used with oversized guide brackets to allow for their sideways motion. Oversized brackets result in loose fit of the rods in the brackets, which, in turn, makes it impossible to assure alignment of the rods with their corresponding stops in the casing of the door or window, unless the stop openings are also oversized. However, if stop openings are oversized, i.e., significantly larger than the locking rods, free play in the entire system inherently results. Such free play is not only crude and unattractive, but it may also permit the closure to slide sufficiently for an intruder to insert a tool to cut the locking rods or shake loose, or otherwise circumvent, the lock.
Another problem which makes prior art devices unsuitable for homeowner installation is the complexity of the techniques needed for positioning the guides for the locking rods. If close fitting guides are used, they must be positioned perpendicularly to the rods to keep the rods from binding when the move through the guides. This problem is aggravated if there is any significant transverse rod movement. But even without such movement, a problem exists when the rod motion is slightly angled from the vertical as, e.g., with the type of lock shown in U.S. Pat. No. 2,969,666. Without a great deal of mechanical aptitude, the average homeowner would simply have to use trial and error techniques to position the guide brackets at the correct degree of tilt from the vertical and at the correct distance from the actuator to guide the rods smoothly. Such need for trial and error installation techniques is obviously an unsuitable selling point for a locking assembly, even aside from the fact that each trial installation defaces the closure frame.
Thus there has been a long felt need for a double-locking assembly for sliding glass closures which can use straight, rigid locking rods positioned to move vertically through guide brackets without any significant transverse component of motion. For simplicity of homeowner installations, a need also exists for such assemblies that are capable of installation without trial and error and without the need for complex positioning measurements. It would also be desirable to use a minimum number of different shapes of parts to simplify the manufacture, storage, distribution and installation of the locking assemblies.